At this point, you need a Pro to size your home. You can still do the install yourself but I'm sure there's more to sizing than what just comes to mind. Brian may not be 'listening' to this post any more so you may need to make a more 'direct move' to get your answers.
No, I don't get any kick-back. Brian has been around for a couple of years and has handled the questions in this area (for FREE just like the rest of us.) I think you can 'trust' his advice even if he's trying to sell to you.